“So you’re not one hundred percent clear on this?” said Aziraphale. “It’s not given to us to understand the ineffable Plan,” said the Metatron, “but of course the Great Plan –” “But the Great Plan can only be a tiny part of the overall ineffability,” said Crowley. “You can’t be certain that what’s happening right now isn’t exactly right, from an ineffable point of view.” “It izz written!” bellowed Beelzebub. “But it might be written differently somewhere else,” said Crowley. “Where you can’t read it.” “In bigger letters,” said Aziraphale. “Underlined,” Crowley added. “Twice,” suggested Aziraphale. “Perhaps this isn’t just a test of the world,” said Crowley. “It might be a test of you people, too. Hmm?” “God does not play games with His loyal servants,” said the Metatron, but in a worried tone of voice. “Whooo-eee,” said Crowley. “Where have you been?”

Quoted in R. Nixon, Six Crises, "Krushchev" (1962) as "In preparing for battle I have always found that plans are useless, but planning is indispensable." Sometimes paraphrased as "Plans are nothing; planning is everything."

The tactical result of an engagement forms the base for new strategic decisions because victory or defeat in a battle changes the situation to such a degree that no human acumen is able to see beyond the first battle. In this sense one should understand Napoleon’s saying: “I have never had a plan of operations.” Therefore no plan of operations extends with any certainty beyond the first contact with the main hostile force.